How to calculate maximum of a dynamic column using arquero (javascript)?

Suppose you have a column name (of table data) in the string variable colname … you can try to do something like

let colname = "something"
data.rollup({
  "max": d => aq.op.max(d[colname])
})

but it won’t work because colname is not defined in that scope.

You might try to escape but that doesn’t work either

let colname = "something"
data.rollup({
  "max": aq.escape(d => aq.op.max(d[colname]))
})

The non-dynamic version does work however.

data.rollup({
  "max": d => aq.op.max(d.something)
})

Is there some way of doing this in arquero? Just a column operation like max, min, mean etc?